1. Field of the Invention
The present invention relates to a powder compression molding machine for producing powder compression molded articles such as drugs, foods and electronic components.
2. Description of the Prior Art
Conventional rotary powder compression molding machines have a rotary table, arranged to rotate horizontally by means of a vertical shaft within a housing. A plurality of dies are arranged at a fixed pitch on this rotary table. Above and below each die is kept an upper punch and a lower punch enabled to slide up and down. The upper punch and lower punch, which have their punch points inserted within the dies, are passed between an upper roller and a lower roller. Generally, the machine is constructed so that the materials, such as drug powders, which fill up the inside of the dies are then compression molded.
In such a powder compression molding machine, the inside of the housing will be depressurized to a pressure lower than atmospheric pressure. For example, Patent Literature 1 (Official Gazette Publication No. Sho 43-25910) discloses one that compresses powder after such depressurization. In such depressurized powder compression molding machines, higher decompressions form better quality molded articles. Thus, the maintenance of the seals becomes important.
In the machine mentioned in Patent Literature 1, a rocker valve is arranged at the part where the powdery material is supplied, as well as at the part where the article is taken out. In this way, the supplying of the powdery material and the taking out of the article are accomplished in a condition where the direct communication between the interior and the exterior is cut off. In other words, this rocker valve has a rotatable partition. After supplying the powdery material at this partition at below atmospheric pressure, the partition is rotated and communicated with a depressurized interior. By this means, the above-mentioned powdery material is supplied to the depressurized interior of the housing.
However, with the above-mentioned rocker valve, at each partition, until the powdery material is supplied to it and to the interior of the housing, a sealed up state must be kept. It is necessary to perfect the tools at the internal circumference and both side surfaces of the rocker valve, in order to completely seal each partition.
However, when employing such tool constructions, the revolving resistance of the tool parts becomes great, when the rocker valve is rotated. This results in remarkable wear of the seals. When the tool sealing up the partition wears away in such an arrangement, the sealing degree within the partition drops. At the spots where the tool function thereby drops, the powdery material may then strongly scatter towards both the air and the interior of the housing. When such a situation occurs, the scattering of the powdery material within the housing interior becomes pervasive, and its cleaning becomes difficult.
Similarly, when a partition having its airtightness deteriorated in this fashion exists at the rocker valve, at the side for taking out the molded article, outside air can flow into the housing interior that has been depressurized, by means of the rocker valve. Thus, the depressurized state can no longer be formed. In this way, because air exists between the particles of the material supplied to the housing interior, the effectiveness of the depressurized compression molding cannot be sufficiently demonstrated.
Additionally, after finishing the compacting of the molded articles in the powder compression molding machine, it is necessary to clean out the powdery material sticking to and remaining within the interior. But, with a depressurized powder compression molding machine, after the molded article is molded and the decompression in the housing is released and opened to the external atmosphere, the powdery material remaining in the housing may scatter to this external atmosphere.
As discussed above, the depressurized powder compression molding machine handles a powdery material within a housing sealed up for airtightness, and compression molding is thereby accomplished to obtain the molded article. However, this process has the problems of maintaining airtightness, as well as the scattering of the internal powdery material when releasing the airtightness.
This invention solves such problems. Its purpose is to present a device that efficiently stops the scattering of the powdery material, while also maintaining the completely sealed up state from the supply of the powdery material and the discharge of the molded article, until the cleaning of the interior.